Process for making alginic acid and product



.rsienaafa' pi; 1, 1936 PROCESS FOR MAKING ALGINIC ACID AND PRODUCTHarland 0. Green, San Diego, Calif assignor to Kelco Company, LosAngeles, Calif., a corporation of Delaware No Drawing. Application April21, 1934, Serial N0. 721,829

20 Claims.

This invention is an improved process of producing an alginic acid fromkelp, and the improved alginic acid and salts of alglnic acid producedby such process. improvement on the process disclosed in the applicationof Clark and Green filed October 16,, 1933 Serial No. 693,891.

Alginic acid is a substance of considerable complexity and is subject toa hydrolytic break- 10 down which proceeds most rapidly when alginicacid is heated in water containing a strong acid, but it also takesplace under many other conditions.

ln Clark and Greens process the aforesaid tendency of the alginic acidto break down is decreased and the viscosity of the alginate solutionincreased, and the protective action of the alginate towards othercolloids enhanced. l have discovered that said process can be so changedand improved as to still further lessen the tendency of the alginic acidto break down and approximately double the viscosity of the alginatesolutions and correspondingly increase the protective action of thealginate.

To enable others to fully understand my improved process and products Iwill describe one complete process of producing insoluble fibrousalginic acid from kelp, which term is intended hil to include marineplants or algae containing alw ginic acid compounds.

times, temperatures, and proportions of reagents used are given; and,where necessary, the range which should be satisfactory is indicated.

(11 Leaching Freshly harvested kelp is placed in a tank of fresh coldwater or cold water which has been acidulated with hydrochloric acid orother suitable acid. The acid is added in the approximate ratio of onegallon per 300 gallons of fresh wa ter. Enough of this mixture is usedto cover all of the kelp. The kelp is left in this mixture approximatelyone hour, after which the mixture is drained off; the leached salts andwatersoluble organic solids being removed with the drained mixture.

' Fresh water is then added to the kelp in the tank and after half anhour is drained oil. The leaching reduces the acid soluble salts andwater soluble organic matter in the kelp so that they will not beoccluded in the subsequent pre cipitation step with the calciumalginate. Such occlusion makes for less efilcient operation as it wouldrequire further acid treatment.

The invention is an In the following specific example the actual Theleaching may be repeated if desired; until the salts and absorbed saltsolutions in the kelp derived from the sea water are sufficientlyremoved. I have used leaching periods of onehalf to 24 hours and findthat the longer the 5 leaching period, the greater the removal of salts.In practice this is determined by ashing samples of the kelp. The kelpas harvested has a total ash or salt content representing about 35-40%of the weight of the solids. The leachl ing is continued until that ashor salt content is reduced to about to 15% of the weight of the solids.

(2) Digesting After leaching, the kelp is chopped into mm M venientlengths to feed to a mill (preferably a Williams hammer mill) equippedwith a A; inch mesh screen. As the kelp is milled, a soda ash (or otheralkaline) solution is added. The method for mixing the milled kelp andthe alkaline solution would be controlled by the equiprnent available.For instance I have first placed the alkaline solution in a tank andmilled the leached kelp into the tank with satisfactory results. anyadequate means of thoroughly mixing the alkaline solution and the milledleached kelp provides very good results. 1 preferably use from to 50pounds of soda ash per ton of freshly harvested kelp in order to obtaina pl-l over 9.6 prior to filtering. As the kelp ages W after harvestingit it is not immediately processed more soda ash is required to give thedesired pH.

1 have found it-very important that the pl-l value of the sodiumalginate liquors resulting 35 from the mixing of sodium carbonatesolution and milled leached kelp be, controlled within certain limits aspreviously mentioned. Fresh kelp contains a relatively large percentageof sugars of diilerent types. Normally a quantity 4d of kelp sumcient tooperate a plant approximately 24 hours is harvested. During the latterpart of this period these sugars are subject to decomposition whichcause a change, upon storage, of the pH value of the kelp. in ordertherefore to keep the pH value of the sodium alginate liquors constantthroughout the 24 hour period while using kelp of varying pH values, itis necessary to slightly increase the amount of soda ash used to producebatches of sodium alginate'liquor having the same pH value. I have foundthat a pH of approximately 10.0 gives optimum filtering andprecipitating results.

The resultant crude sodium alginate solution is added to sufficientpermutited or tap water (of about 50 F.) to enable it to be pumped andagitated; usually about one hundred gallons of water per ton of raw kelpis used. Digestion starts as soon as the kelp and soda ash are mixed andrequires about one-half hour; but the mixture has been left for as muchas 24 hours without loss of viscosity due to the low temperatureemployed, (approximately 50 F.) In the Clark- Green process thetemperature in the digesting step is about 180 F. and slight variationsin the time of primary digestion markedly alters the viscosity and yieldof the finished product.

It should be understood that soda ash (sodium carbonate) is used abovesimply as illustrative, as alkalies other than sodium carbonate may beemployed in the digestion step above described within the scope of theinvention.

The sodium alginate solution is then milled a second time (preferably inthe Williams mill) through a 30 mesh screen. This second milling insurescomplete digestion but is not vital to the operation. This milling isaccomplished by pumping the kelp to a tank and allowing it to fiow intoand through the mill. I have determined that the reaction continues fromthe time the milled leached kelp first comes in contact with the sodiumcarbonate solution until the time when that solution has been diluted,filtered and precipitated. In other words, I consider the totaldigesting time to be the period from when the sodium carbonate solutionand kelp are mixed together, up to the time when the alginate isprecipitated by calcium chloride as calcium alginate. Variations inyield and in breakdown of the algin molecules can be very closelypredetermined by varying the time and temperature of the material duringthis period.

(3) Separation of fibrous calcium alginate The sodium alginate solutionis then diluted with cold permutited water in approximately a 1:6 ratioand agitated thoroughly to insure good dispersion. This dilution is donemerely to aid filtration. Permutited water is used to prevent theformation of insoluble calcium alginate found in using tap water; suchformation is undesirable as it causes ineflicient filtration and loss ofyield. The temperature during this stage is kept at about 50 F.; whereasat this stage in the Clark-Green process a temperature of about 120 F.is maintained. The pH is about 9.6 to 11, slightly higher than in theClark-Green process.

To make my cold process method successful it is necessary to preventbacterial decomposition. Bacteria enter with the kelp, the air, orreagents used; and if allowed to react for sufficient time they cause abreak down of the sugars and algin present. The bacterial growth can bemeasured by observation of the pH of the diluted liquor and also by theodor of the liquor. Such growth materially destroys the viscosity,efficiency and yield of the alginate. I have found I can control thebacteria by (1) using clean tanks which are disinfected when necessaryby chlorine or other suitable means, (2) keeping the temperature lowand, (3) further processing the material immediately, if bacterialdecomposition sets in, to prevent further decom-- position. The dilutedliquor is preferably filtered, immediately after dilution, in order topre vent this bacterial growth; but I have successfully made alginicacid even after the liquor has stood several hours.

To filter, the unfiltered liquor is pumped into a tank and filter-aid,such as diatomaceous silica, added thereto: the mixture is then pumpedthrough a mechanical filter press. The use of such filter-aid gives amore brilliant and purer alginate than obtained by any other separationmeans, as all of the cellulose and other insoluble constituents areremoved. The temperature during this filtering step is approximately 50F. whereas during the corresponding step in the Clark-Green process thetemperature is about 120 F.

In this particular filtering step steam might be applied to the tankwherein the filter-aid is added to slightly raise the temperature of theliquor previous to passing it through the filter press, as this willreduce the viscosity of the material so that filtration can beaccomplished more quickly and cheaper. Such temperature increase,approximately from 50 to 120 F., is only temporary, and only done withdilute liquor and the filtered liquor is cooled after leaving the press;or the precipitated calcium alginate (see next step) is cooled bywashing with cold water.

While I prefer to separate the insoluble matter from the sodium alginateliquor by using filter aid and a mechanical filter press, other methodscould be used, such as centrifuging, vacuum filtering, sand bedfiltration and straight gravity settling of the cellulose when theliquor is very dilute.

For some purposes the presence of cellulose in sodium and ammoniumalginates is not objectionable. The same improvement in the quality ofthe alginic acid as compared to former types of alginic acid is obtainedwhether or not the cellulose is removed from the liquor. It is myintention to manufacture sodium alginate by my process including thefiltration for the removal of insoluble matter for the food industry,and to also manufacture other grades of sodium alginate and ammoniumalginate by my process without removing the cellulose for otherindustries where the use will be industrial applications. In other wordsthe increased value or improvement obtained by this new process and theoutstanding differences in the properties of the products manufacturedby my process as compared to other processes is not in any way dependentupon whether the cellulose is removed from the liquor or not. Thisoptional step is only dependent upon the application for which theproduct is being prepared.

(4) Production of insolubleflbrous calcium alginate After filtration theliquor is added slowly to an agitated solution of preferably calciumchloride in about the proportions of about 100 lbs. of calcium chlorideand 800 lbs. of water per 8 tons of the liquor. This results in theformation of an insoluble salt of alginic acid. The stated proportionswill vary directly with variations in the sodium alginate concentrationadded to remove the kelp flavor, and impart the desired whiteness to thematerial.

The amount of bleach used is dependent upon the color of precipitatebefore bleaching. This color in turn is dependent upon the color of thesodium alginate liquor used for precipitating. I have found that thelarger the concentration of sodium carbonate used for the digestionand/or the longer the period of digestion and/or the higher thetemperature of digestion, the darker the dolor of sodium alginate liquorresulting from the reaction. The. controlling factor on the color afterbleaching the calcium alginate' is the color of the solution which ismade from the finished salt, such as sodium or ammonium alginate. I havefound that this solution color varies directly with the color of thecalcium alginate before acid treating.

One of the outstanding advantages of my process is that since the sodiumalginate liquor to be precipitated is made at low temperature thecalcium alginate precipitated from the liquor is of much lighter colorthan the calcium alginate made from liquors produced under formerprocesses. This means therefore that a considerably smaller amount ofbleach is required to lighten the color of calcium alginate produced bythis process to a given color standard than is required with formerprocesses. An average amount of bleach to be used in this process tolighten the color of the calcium alginate sufficiently to produce afinished salt that will give a very light solution color is about 20pounds of bleach in one ton of water. i

I have found that one of the serious factors causing breakdown of themolecular sizes of the alginic acid recovered is the amount of bleachused. The difference therefore in the natural color of the calciumalginate precipitated by my cold process as compared to previousprocesses contributes to a large extent to the improvement in theresultant alginic acid obtained because of the fact that less bleach isrequired.

() Conversion into fibrous alginic acid Following bleaching, theprecipitate is separated from the surplus water. The precipitate is thenintroduced into a dilute hydrochloric acid solution in the proportion ofapproximately 100 pounds of the precipitate, anhydrous basis, to 200pounds of hydrochloric acid in 4000 pounds of water whereby the fibrouscalcium alginate is converted into fibrous alginic acid.

The admixture is then passed through a suitable screen to remove theexcess acid solution and the calcium chloride formed by the reaction ofthe hydrochloric acid and calcium alginate. The drained precipitate isthen added to a second tank of water containing dilute hydrochloricacid, agitated for a short time and then pumped over another screen.This treatment is repeated until the precipitate is washed free ofcalcium salts. Enough fresh or permutited water is used in the washingto render the pH of the acid over 1.9 and at the same time reduce theamount of the ash or calcium contained in the fiber. V

The pure alginic acid may then be concentrated either by means of apress or filter. It is then immediately stored in a refrigerated room.

In my new process the use of heat in 'the extraction of the algin ispractically eliminated and the resulting alginate is so much more freefrom breakdown that only about-40% to 50% as much is required incommercial uses as heretofore required with the conventional type ofalginate that has been produced heretofore. My process requires noadditional heat as heretofore required in the extraction of algin fromkelp, and while the optional use of heat as an aid in the filtrationstep is mentioned above, so

little heat would ever be used for that purpose and even then for soshort a time, that it can be considered to have substantially no effecton the reaction at that point. The optional use of heat at that point ismerely a detail of filtering. By the Woolwich method of determiningviscosities myv new improved products have a viscosity ranging from 400to 2000 seconds on a 1% solution, as compared to the old conventionaltype of alginates that have a viscosity of 5 to 10 seconds on a 2%solution. Briefly the Woolwich viscosity method consists in putting thesolution under test in a long vertical test tube about one centimeter indiameter and decrease in the viscosity of the finished product but alsoa loss in yield.

I have found that a temperature over 120 F. has caused decomposition andloss of the entire precipitate. In the foregoing process I operate atapproximately 50 F., but intend to further reduce this temperature to afew degrees above the freezing point.

In the Clark-Green process steam or other heat is used; whereas I avoidheat and employ mechanical means to break up and mix cold kelp with acold alkali to cause digestion, and thereby maintain colder temperaturesthroughout the process.

My cold process reduces the rate of hydrolytic break down attending theClark-Green process and is less sensitive in regard to length of timeduring digestion and dilution prior to filtration. It also enables me toconsistently produce a more uniform and higher viscosity alginic acidthan heretofore obtained. Thus a steel ball 1/ 16 of an inch in diameterwill fall 15 centimeters in approximately 800 seconds when dropped in a2% solution of ammonia alginate made by the Clark-Green process; whereasthe ball will be suspended over 800 seconds in a 1% solution of myimproved alginate.

Also whereas .18% of Walsh-Thornleys product (Patent No. 1,814,981) or.10% of the prodnot of the Clark-Green process is required to give acertain suspension of cocoa in chocolate milk; only .08% of the productof my improved process is required. And, in general, the aqueoussolutions of salts of alginic acid produced by my improved processpossess higher viscosities and have greater efficiency in producingdispersions of insoluble solids and liquids than alginates heretoforeobtained in the extraction of alginic acid from kelp by prior processes.

My new product can be used in all the present uses of alginates and doesthe same work more efficiently. Some special uses are: (l) creaminglatex, (2)

suspending and emulsifying autopolish, and (3) as a stabilizer in icecreams, ice milk, sherbets and ices.

Algin produced by my process has shown a viscosity as determined by theWoolwich method, by using a 1% solution instead of a 2% solution, ofover 800 seconds. It is impractical to attempt to measure the viscosityo1 a 2% solution by this method. The viscosity of a one-half of 1%solution ranges from 20 to 30 seconds.

An essential difference between my process to obtain this material andthe Clark and Green process is that heat is not used as required intheir process. Instead of cooking the kelp in a solution of sodiumcarbonate I mill the leached kelp into a cold solution of sodiumcarbonate where it is agitated for a few minutes, when the resultingcrude solution of sodium alginate is again milled through a very finescreen. In addition to this I have further reduced the time of leachingin cold water, the first leach water containing a small amount ofhydrochloric acid, and have also reduced the time of acid treating thecalcium alginate with hydrochloric acid.

Another difference is that the solution color of ammonium or sodiumalginate made without any bleach is much lighter when made by my processthan by former processes. Furthermore, a still lighter color may beobtained by adding a much smaller amount of bleach to the calciumalginate made by my process than made by former processes. This resultsin less breakdown of the size of the algin molecule by the bleach thanin former processes.

My process also makes possible higher recoveries than any hot process.During the digestion of the kelp plant which is going on from the timethe sodium carbonate is added to the milled leached kelp up to the timethe liquor has been precipitated into calcium alginate the material iskept cool throughout. This is in. sharp contrast with former processes.As commonly known the speed of a chemical reaction varies withtemperature, and close control of my process is much less critical thanof the hot processes. This is borne out by the fact that by my processmuch larger molecules are obtained in the finished alginic acid. The hotdigestion used in former processes results not only in reducing the sizeof the molecules of the recovered alginate but the amount of alginicacid recovered from a given amount of kelp is greatly reduced. .Muchhigher recoveries of alginic acid from given quantities of kelp arepossible under practical operating conditions with my cold process thanwith hot processes because the reaction going on between the sodiumcarbonate and the algin in the kelp is much less critical to control andbecause the operator can quite easily decide when to precipitate thesodium alginate liquor to obtain the largest yield of calcium alginate.The yield of calcium alginate obtained from the sodium alginate liquoris much more a question of chance when using a hot process than whenusing my cold process.

Comparative tests of my product have shown that for some purposes it isapproximately four times more efllcient than the old conventionalalginates and about twice as efllcient as the alginates produced by theClark and Green process.

I claim:

1. The herein described cold process of proparing alginic acid,consisting in cold leaching kelp, digesting the leached kelp in analkaline solution without addition of heat, comminuting the digestedpulp, diluting the comminuted pulp with cold water and filtering themixture, mixing the filtrate with a cold solution of a salt that willprecipitate an insoluble salt of alginic acid from a sodium alginatesolution, separating the resultant insoluble precipitated alginate,subjecting the alginate to a cold solution of an acid capable of forminga soluble salt with the mineral constituent of the insoluble alginate,and finally separating the free alginic acid and washing it with coldwater.

2. The herein described cold process of preparing alginic acid,consisting in cold leaching fresh kelp, digesting the leached kelp in analkaline solution to which no heat is added, and comminuting thedigested pulp, diluting the comminuted pulp with cold water andfiltering the mixture, mixing the filtrate with a cold calcium chloridesolution to precipitate calcium alginate, separating the resultantcalcium alginate, subjecting the alginate to a cold solution of an acidcapable of forming a soluble salt with the mineral constituent of theinsoluble alginate, and finally separating the free alginic acid andwashing it with cold water.

3. The herein described cold process of preparing fibrous alginic acid,consisting in leaching fresh kelp in a cold solution of a soluble acidwhich at the concentration prevailing in the diluted liquor does notform a precipitate with the subsequently added calcium chloridesolution, digesting the leached kelp in a cool solution containingsodium carbonate and comminuting the digested pulp, diluting thecomminuted pulp with cold water and filtering the mixture, mixing thefiltrate with a calcium chloride solution, separating the resultingfibrous calcium alginate, subjecting the alginate to a cold solution ofhydrochloric acid, and finally separating the free fibrous alginic acidand washing it with cold water.

4. The herein described cold process of pre paring fibrous alginic acid,consisting in leaching fresh kelp in a cold solution of a soluble acidwhich at the concentration prevailing in the diluted liquor does notform a precipitate with the subsequently added calcium chloridesolution, digesting the leached kelp in a cold solution containingsodium carbonate, comminuting the digested pulp, diluting the comminutedpulp with cold water and filtering the mixture, mixing the filtrate witha calcium chloride solution, separating the liquor from the resultantfibrous calcium alginate, bleaching the fibrous alginate and washingitswith cold water, subjecting the bleached alginate to a cold solutionof hydrochloric acid, separating said alginate from the solution andwashing it with cold water.

5. The process of producing alginic acid, consisting in leaching freshlyharvested kelp in a cold solution of dilute hydrochloric acid to removethe salts and absorbed salt solutions, milling the kelp and digestingthe same in a cold solution of soda ash, milling the resultant paste anddiluting. it with cold Water and filtering, mixing the filtrate with acold solution of calcium chloride to produce fibrous calcium alginate,separating the precipitated alginate and treating same with a coldsolution of hydrochloric acid, and finally separating the insolublealginic acid from the solution and washing same.

6. The herein described process of producing alginic acid consisting inleaching freshly harvested kelp in a cold solution of dilutehydrochloric acid to remove the salts and absorbed salt solutions,milling the kelp and digesting the aoaaosa same in a cold solution ofsoda ash, milling the resultant; paste and diluting it with cold waterand filtering, mixing the filtrate with a cold solution of calciumchloride to produce fibrous calcium alginate, bleaching the fibrouscalcium alginate, separating the precipitated alginate and treating samewith a cold solution of hydrochloric acid, and finally separating theinsoluble alginic acid from the solution, and washing same.

7. The herein described alginic acid whose sodium salt in aqueoussolution will produce dispersions of insoluble liquids, and solids, andwhose ammonium salt at a concentration of 1% in an aqueous solution hasa viscosity, as determined by the Woolwich method, of over 800 seconds.

8. The herein described fibrous alginic acid produced by cold leachingkelp, digesting the leached kelp in a cool alkaline solution,comminuting the digested kelp and diluting it with cold water andfiltering same. precipitating an insoluble alginate in the filtrate byadding a cold solution of a. salt whose metallic radical ion forms aninsoluble precipitate with alginate ion, separating the insolubleprecipitated alginate, subjecting it to a cold solution of an acidcapable of forming a soluble salt with the mineral constituent of theinsoluble alginate, and finally separating and washing the free alginicacid.

9. The herein fibrous alginic acid produced by leaching fresh kelp in acold solution of a soluble acid which at the concentration prevailing inthe diluted liquor does not form a precipitate with the subsequentlyadded calcium chloride solution, digesting the leached kelp in a coolsolution containing sodium carbonate, comminuting the digested pulp,diluting it with cold water and filtering it, mixing the filtrate with acalcium chloride solution, separating the resultant fibrous calciumalginate and subjecting it to a cold solution of hydrochloric acid, andfinally separating the free fibrous alginic acid and Washing it.

10. The herein described fibrous alginic acid, of which an aqueous onepercent ammonia alginate solution will have a viscosity as determined bythe Woolwich method of over 800 seconds.

11. The herein described cold process of preparing fibrous alginic acid,consisting in. leaching fresh kelp in a cold solution of a soluble acidwhich at the concentration prevailing in the diluted liquor does notform a precipitate with the subsequently added calcium chloridesolution, digesting the leached kelp to a pulp in a cold solutioncontaining sodium carbonate, comminuting the digested pulp, diluting thecomminuted pulp with cold water, filtering the mixture, mixing thefiltrate with a calcium chloride solution to precipitate fibrous calciumalginate, separating the resultant fibrous calcium alginate, subjectingsuch fibrous alginate to a cold solution of hydrochloric acid, andfinally separating the free fibrous alginic acid and washing it withcold water.

12. The herein described cold process of preparing fibrous alginic acid,consisting in leaching fresh kelp in a cold solution of a soluble acid.which at the concentration prevailing in the diluted liquor does notform a precipitate with the subsequently added calcium chloridesolution, digesting the leached kelp to a pulp in a cold solutioncontaining sodium carbonate, comminuting the pulp, diluting thecomminuted pulp with cold water,-filtering the mixture, mixing thefiltrate with a calcium chloride solution to precipitate fibrous calciumalginate, separating the liquor from the resultant fibrous calciumalginate, bleaching theflbrous alginate, washing it with cold water,subjecting the bleached and washed alginate to a cold solution ofhydrochloric acid, separating said alginate from the solution, andwashing it with cold water.

13. The herein described fibrous alginic acid produced by cold leachingkelp, digesting the leached kelp to a pulp in a cool alkaline solution,comminuting the digested pulp, diluting it with cold water and filteringsame, precipitating the alginate ion in the solution by a cold solutionof a salt whose metallic radical ion forms an insoluble precipitate withalginate ion, separating the insoluble precipitated alginate, subjectingsuch alginate to a cold solution of hydrochloric acid, separatingv theinsoluble alginic acid and washing it.

14. The herein described fibrous alginic acid produced by leaching freshkelp in a cold dilute solution of an inorganic acid, digesting theleached kelp in a cold solution containing sodium carbonate, comminutingthe digested pulp, diluting it with cold water and filtering it, mixingthe filtrate with a calcium chloride solution to precipitate calciumalginate, separating the resultant fibrous calcium alginate from thesolution and subjecting such alginate to a cold solution of hydrochloricacid, finally separating the free fibrous alginic acid, and washing it.

15. The herein described cold process of preparing alginic acidconsisting in cold leaching kelp, digesting the leached kelp in analkaline solution withoutaddition of heat, comminuting the digestedpulp, mixing the comminuted pulp with a cold solution of a salt thatwill precipitate an insoluble salt of alginic acid from a sodiumalginate solution, separating the resultant insoluble precipitatedalginate, subjecting the alginate to a cold solution of an acid capableof forming a soluble salt with the mineral constituent of the insolublealginate and finally separating the free alginic acid and washing itwith cold water.

16. The herein described process of producing alginic acid consisting inleaching freshly harvested kelp in a cold solution of dilutehydrochloric acid to remove the salts and absorbed salt solutions,milling the kelp and digesting the same in a cold solution of soda ash,milling the resultant paste, mixing the milled paste with a coldsolution of calcium chloride to produce fibrous calcium alginate,bleaching the fibrous calcium alginate, separating theprecipitatedalginate and treating same with a cold solution of hydrochloric acid,and finally separating the insoluble alginic acid from the solution, andwashing same.

17. The herein described fibrous alginic acid produced by cold leachingkelp, digesting the leached kelp in a cool alkaline solution,comminuting the digested kelp, precipitating an insoluble salt ofalginic acid from the comminuted kelp by a cold salt solution whosemetallic ion form an insoluble precipitate with an alginate ion,separating the insoluble precipitated alginate, subjecting it to a coldsolution of an acid capable of forming a soluble salt with the mineralconstituent of the insoluble alginate, and finally separating the freealginic acid and washing it.

18. The herein described cold process of preparing fibrous alginic acid,consisting in leaching fresh kelp in a cold solution of a soluble acidwhich at the concentration prevailing in the diluted liquor does notform a precipitate with the subsequently added calcium chloridesolution, digesting the leached kelp to a pulp in a cold solutioncontaining sodium carbonate, comminuting the digested pulp, mixing thedigested pulp with a calcium chloride solution to precipitate fibrouscalcium alglnate, separating the resultant fibrous calcium alginate,subjecting such fibrous alginate to a cold solution of hydrochloricacid, and finally separating the free fibrous alginic acid and washingit with cold water.

19. The herein described fibrous alginic acid produced by cold leachingkelp, digesting the leached kelp to a pulp in a cool alkaline solution,comminuting the digested pulp, precipitating the alginate ion in thepulp by a cold solution of a salt whose metallic ion forms an insolubleprecipitate with an alginate ion, separating the insoluble precipitatedalginate, subjecting it to a cold acid solution capable of forming asoluble salt with the mineral constituent of the insoluble alginate, andfinally separating the 5 insoluble alginic acid and washing it.

20. The herein described fibrous alginic acid produced by cold leachingkelp, digesting the leached kelp to a pulp in a cool alkaline solution,comminuting the digested pulp, precipitating 1 the alginate ion in thepulp as an insoluble alginate by a cold solution of a salt whosemetallic radical ion forms an insoluble precipitate with alginate ion,separating the insoluble precipitated alginate, subjecting such alginateto a 1 cold solution of hydrochloric acid, and separating and washingthe insoluble alginic acid.

HARLAND C. GREEN.

